Common name(s): Carpenter bee
A large bee, reaching slightly more than 20mm. Female is mainly black. The thorax is covered with deep yellow hairs, making it almost fully yellow except for a small black patch in the centre. The male, on the other hand, is covered with fine yellow hairs, making him fully dark yellow.
This species is quite widely distributed across Southeast Asia, and is one of the commonly seen species in Singapore. In Singapore and surrounding regions, this species and similar-looking species are often misidentified as Xylocopa confusa. Another very similar species in Singapore is Xylocopa flavonigrescens - the female of this species looks nearly identical to Xylocopa aestuans and can only be separated by looking closely at certain characters such as the colour of the genal hairs and the shape of the basitibial plate (a smooth shiny plate found on the tibia) of the hind legs. I will provide information on how to separate them once I take photos of the characters in question. Males of Xylocopa flavonigrescens look different from males of Xylocopa aestuans.
Females of this species are commonly seen feeding from flowers in parks and even schools (many schools in Singapore build and maintain gardens as part of the science syllabus or to encourage responsibility in students). The male is less often seen, since he usually chooses one particular spot and guards it vigorously. Males of this species are the most territorial of the carpenter bees I have observed, and also occupy their territories for very long periods. They will hover and stare down intruders much larger than themselves, even humans! However, they sure know when to beat a hasty retreat, and are alert to movement; a sudden movement towards a male will cause him to disappear at top speed.
This species is quite versatile in choice of nesting sites. However, I noticed that it seldom ever attacks well-maintained surfaces; all man-made structures I found nests in had been neglected for a long time and the wood was starting to break up. In more natural environment, they frequently nest in tree stumps and fallen logs.